Method and apparatus for carrier assignment, configuration and switching for multicarrier wireless

ABSTRACT

As part of carrier assignment and configuration for multicarrier wireless communications, a single uplink (UL) primary carrier may provide control information for multiple concurrent downlink (DL) carriers. Optionally, control information for each DL carrier may be transmitted over paired UL carriers. Carrier switching of UL and/or carriers, including primary and anchor carriers, may occur during normal operation or during handover, and may occur in only the UL or only the DL direction. A unidirectional handover is performed when only an UL carrier or only a DL carrier is switched as part of a handover. Switching of UL and/or DL carriers may be from one component carrier or a subset of carriers to another component carrier, another subset of carriers, or all carriers in the same direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/160,106 filed Mar. 13, 2009, and U.S. Provisional Application No.61/160,513 filed Mar. 16, 2009 which are incorporated by reference as iffully set forth.

FIELD OF INVENTION

This application is related to wireless communications.

BACKGROUND

In multicarrier communications, reporting of downlink (DL) controlinformation on the uplink (UL) is typically done for one DL carrier at atime. Therefore, existing multicarrier communication systems are lackingtechniques for reporting control information on the UL for multipleconcurrent DL carriers.

An example multicarrier wireless communications system is the ThirdGeneration Partnership Project (3GPP) long term evolution (LTE) systemthat has been introduced into 3GPP Release 8 (R8). The LTE DLtransmission scheme is based on an Orthogonal Frequency DivisionMultiple Access (OFDMA) air interface. According to OFDMA, a wirelesstransmit/receive unit (WTRU) may be allocated by the evolved Node B(eNB) to receive its data anywhere across the whole LTE transmissionbandwidth. For the LTE uplink (UL) direction, single-carrier (SC)transmission is used based on discrete Fourier transform-spread-OFDMA(DFT-S-OFDMA), or equivalently, single carrier frequency divisionmultiple access (SC-FDMA). A WTRU in the UL may transmit only on alimited, yet contiguous set of assigned sub-carriers in an FDMAarrangement. FIG. 1 illustrates the mapping of a transport block 102 toan LTE carrier 110, for UL or DL transmission. Layer 1 (L1) 106 receivesinformation from the hybrid automatic repeat request (HARQ) entity 104and the scheduler 108, and uses it to assign a transport block 102 to anLTE carrier 110. As shown in FIG. 1 , an UL or DL LTE carrier 110, orsimply a carrier 110, is made up of multiple sub-carriers 112. An eNBmay receive a composite UL signal across the entire transmissionbandwidth from one or more WTRUs at the same time, where each WTRUtransmits on a subset of the available transmission bandwidth orsub-carriers.

LTE-Advanced (LTE-A) is being developed by the 3GPP standardization bodyin order to further improve achievable throughput and coverage ofLTE-based radio access systems, and to meet the International MobileTelecommunications (IMT) Advanced requirements of 1 Gbps and 500 Mbps inthe DL and UL directions, respectively. Among the improvements proposedfor LTE-A are carrier aggregation and support of flexible bandwidtharrangements. LTE-A proposes to allow DL and UL transmission bandwidthsto exceed the 20 MHz limit in R8 LTE, for example, permitting 40 MHz or100 MHz bandwidths. In this case, a carrier may occupy the entirefrequency block.

LTE-A proposes to allow for more flexible usage of the available pairedspectrum, and is not limited to operate in symmetrical and paired FDDmode, as in R8 LTE. LTE-A proposes to allow asymmetric configurationswhere, for example, a DL bandwidth of 10 MHz may be paired with an ULbandwidth of 5 MHz. In addition, LTE-A proposes composite aggregatetransmission bandwidths, which may be backwards compatible with LTE. Byway of example, the DL may include a first 20 MHz carrier plus a second10 MHz carrier, which is paired with an UL 20 MHz carrier. Carrierstransmitted concurrently in the same UL or DL direction are referred toas component carriers. The composite aggregate transmission bandwidthsof the component carriers may not necessarily be contiguous in thefrequency domain. For example, the first 10 MHz component carrier may bespaced by 22.5 MHz in the DL band from the second 5 MHz DL componentcarrier. Alternatively, contiguous aggregate transmission bandwidths maybe used. By way of example, a first DL component carrier of 15 MHz maybe aggregated with another 15 MHz DL component carrier and paired withan UL carrier of 20 MHz. FIG. 2 shows a discontinuous spectrumaggregation with component carriers 205, and FIG. 3 shows a continuousspectrum aggregation with component carriers 305.

FIG. 4 illustrates a reserved time-frequency location for thetransmission of the physical uplink control channel (PUCCH) according toLTE R8. PUCCH is used for transmitting control data on the uplink. FIG.4 shows one subframe made up of two timeslots 402, where N_(RB) ^(UL)denotes the number of resource blocks (RBs) available for uplinktransmission and n_(PRB) is the RB index. RBs on the edges of thefrequency spectrum may be used for PUCCH transmission, and RBs on theopposite edges may be used in the two time slots to improve thediversity. By way of example, a WTRU may use the RBs indicated by m=1for PUCCH transmission. The control data carried by PUCCH may include,but is not limited to, acknowledge/negative acknowledge (ACK/NACK)information for the DL transmission, scheduling requests (SRs), channelquality indicator (CQI) information to enable scheduling for DLtransmission, rank indicator (RI) information, and preceding matrixindicator (PMI) information to enable MIMO operation. Herein, the termCQI is generalized to also include PMI and RI. According to LTE R8,PUCCH used for CQI reporting and PUCCH used for scheduling requests(SRs) are configured to be periodic, such that each PUCCH reportsinformation for only one downlink carrier.

The PUCCH configuration in LTE R8 is designed for one component carrier.Therefore, it is desirable to develop new configurations for PUCCH forLTE-A with carrier aggregation, where more than one component carriermay be transmitted at a time in the DL, while supporting CQI (includingPMI and RI) reporting for multiple downlink carriers, and efficient SRreporting with low impact from discontinuous reception (DRX) cycles onmultiple carriers. More generally, it is desirable to develop techniquesfor simultaneous reporting of information for multiple concurrent DLcarriers in multicarrier communications systems.

A multicarrier system employing carrier aggregation, such as LTE-A, mayinclude anchor and non-anchor component carriers. This may reduce theoverhead because system information, synchronization and paginginformation for a cell may be transmitted on anchor carrier(s) only. Theanchor carrier(s) may enable synchronization, camping and access in aheterogeneous network environment where interference coordination may beprovided for at least one detectable or accessible anchor carrier.

Multiple carriers may exist in the DL and UL for carrier aggregation.However, the carrier quality may change and/or the amount of DL or ULtraffic may change in a dynamic or semi-persistent way. Thus, it wouldbe desirable to provide flexible and efficient DL and UL componentcarrier assignment and switching to provide improved utilization andtransmission quality for multiple carrier systems employing carrieraggregation, such as LTE-A.

SUMMARY

A method and apparatus for carrier assignment, configuration andswitching for multicarrier wireless communications are disclosed. Asingle uplink (UL) primary carrier may provide control information formultiple concurrent downlink (DL) carriers. Optionally, DL carriers maybe paired with UL carriers, such that control information for each DLcarrier is transmitted over its paired UL carrier. Carrier switching ofUL and/or DL carriers, including primary and anchor carriers, may beinitiated by the wireless transmit/receive unit (WTRU) or the evolvedNode B (eNB) and may occur during normal operation or during handover.Switching of carriers in only the UL or only the DL direction may occur.A unidirectional handover is performed when only an UL carrier or only aDL carrier is switched as part of a handover. Switching of UL and/or DLcarriers may be from one component carrier to another component carrier,a subset of carriers, or all carriers in the same direction.Alternatively, carrier switching may be from a subset of carriers to onecomponent carriers, another subset of carriers, or all the carriers inthe same direction.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1 shows a mapping of a transport block to an LTE carrier accordingto LTE R8;

FIG. 2 shows a discontinuous spectrum aggregation according to LTE-A;

FIG. 3 shows a continuous spectrum aggregation according to LTE-A;

FIG. 4 shows an LTE PUCCH structure;

FIG. 5 shows an example wireless communication system including aplurality of wireless transmit/receive units (WTRUs) and an evolved NodeB (eNB);

FIG. 6 shows an example functional block diagram of a WTRU and eNB ofFIG. 5 ;

FIG. 7 shows an UL primary carrier for DL control information;

FIG. 8 shows pairing of UL and DL carriers for transmitting DL controlinformation on the UL;

FIG. 9 shows a flow diagram for using an uplink primary carrier fortransmitting control information for a set of DL component carriers;

FIG. 10 shows a flow diagram for pairing UL and DL carriers fortransmitting control information of DL component carriers on the UL;

FIGS. 11A, 11B, 12A and 12B show examples of carrier switching on acommon eNB; and

FIGS. 13A, 13B, 14A and 14B show examples of carrier switching from oneeNB to another eNB, referred to as unidirectional handovers.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. Whenreferred to hereafter, the terminology “base station” includes but isnot limited to a Node-B, a site controller, an access point (AP), or anyother type of interfacing device capable of operating in a wirelessenvironment.

The embodiments described herein are applicable to any system employingmulti-carrier communications including, but not limited to, orthogonalfrequency divisional multiple access (OFDMA) and orthogonal frequencydivisional multiplexing (OFDM). Examples of wireless communicationssystems employing multicarrier communications include, but are notlimited to, Long Term Evolution (LTE), LTE Advanced (LTE-A), Instituteof Electrical and Electronic Engineers (IEEE) 802.11, IEEE 802.16m, andWorldwide Interoperability for Microwave Access (WiMAX). The embodimentsbelow are described by way of example based on LTE and LTE-A technology,but are not limited to these technologies and can be applied to anymulti-carrier communications system. Feedback information and/or controlinformation is referred to herein as control information.

FIG. 5 shows a Long Term Evolution (LTE) wireless communicationsystem/access network 500 that includes an Evolved-Universal TerrestrialRadio Access Network (E-UTRAN) 505. The E-UTRAN 505 includes severalevolved Node-Bs, (eNBs) 520. The WTRU 510 is in communication with aneNB 520. The eNBs 520 interface with each other using an X2 interface.Each of the eNBs 520 interface with a Mobility Managements Entity(MME)/Serving GateWay (S-GW) 530 through an S1 interface. Although asingle WTRU 510 and three eNBs 520 are shown in FIG. 5 , it should beapparent that any combination of wireless and wired devices may beincluded in the wireless communication system access network 500.

FIG. 6 is an example block diagram of an LTE wireless communicationsystem 600 including the WTRU 510, the eNB 520, and the MME/S-GW 530. Asshown in FIG. 6 , the WTRU 510, the eNB 520 and the MME/S-GW 530 areconfigured to perform a method of carrier assignment and switching formulticarrier wireless communications.

In addition to the components that may be found in a typical WTRU, theWTRU 510 includes a processor 616 with an optional linked memory 622, atleast one transceiver 614, an optional battery 620, and an antenna 618.The processor 616 is configured to perform a method of carrierassignment and switching for multicarrier wireless communications. Thetransceiver 614 is in communication with the processor 616 and theantenna 618 to facilitate the transmission and reception of wirelesscommunications. In case a battery 620 is used in the WTRU 510, it powersthe transceiver 614 and the processor 616.

In addition to the components that may be found in a typical eNB, theeNB 520 includes a processor 617 with an optional linked memory 615,transceivers 619, and antennas 621. The processor 617 is configured toperform a method of carrier assignment and switching for multicarrierwireless communications. The transceivers 619 are in communication withthe processor 617 and antennas 621 to facilitate the transmission andreception of wireless communications. The eNB 520 is connected to theMobility Management Entity/Serving GateWay (MME/S-GW) 530 which includesa processor 633 with an optional linked memory 634.

In a first embodiment, control information for any number of DL carriersmay be provided on a single UL carrier, referred to herein as theprimary UL carrier. The primary carrier may be an UL anchor carrier orany other type of UL carrier. The primary carrier may be defined as thecarrier assigned to carry the control information for the DL carriers.Optionally, there may be multiple primary carriers such that each DLcarrier is paired with an UL carrier, so that control information foreach DL carrier may be transmitted on its corresponding primary carrier.

FIG. 7 shows an UL primary carrier for DL control information 700, inaccordance with the teachings herein. In FIG. 7 , a single UL primarycarrier 704 is used to carry the control information for one or more DLcomponent carrier 702. Non-primary uplink carriers 706 may not be usedto transmit control information for downlink carriers 702. The primaryUL carrier 706 may be an UL anchor carrier, or any other UL carrier.

FIG. 8 shows pairing of UL and DL carriers for transmitting controlinformation on the UL 800, in accordance with the teachings herein. InFIG. 8 , each DL carrier 802 _(a), 802 _(b), . . . , 802 _(n) is pairedwith a corresponding UL carrier 806 _(a), 806 _(b), . . . 806 _(n), suchthat control information for each DL carrier 802 _(a), 802 _(b), . . .802 _(n) is transmitted on the corresponding paired UL carrier 806 _(a),806 _(b), 806 _(n).

FIG. 9 shows a flow diagram 900 for using an uplink primary carrier fortransmitting control information for a set of DL component carriers, inaccordance with the teachings herein. At 905, the WTRU receives firstconfiguration information for a set of UL carriers and a set of DLcarriers. The first configuration information may be included in one orseveral different messages. For example, the configuration informationfor the set of UL carriers may be received in a separate message fromthe configuration information for the set of DL carriers, or a differentsubset of UL carriers. At 910, the WTRU configures the set of ULcarriers and the set of DL carriers according to the first configurationinformation. At 915, the WTRU receives second configuration informationfor an UL primary carrier. The first and second configurationinformation may be received in a common message, or in separatemessages. At 920, the WTRU configures the UL primary carrier accordingto the second configuration information. At 925, the WTRU receivesmessages over the set of DL carriers. At 930, the WTRU transmits controlinformation for the set of DL carriers on the UL primary carrier. TheWTRU may transmit control information for all or a subset of the set ofDL carriers over the UL primary carrier.

FIG. 10 shows a flow diagram 1000 for pairing UL and DL carriers fortransmitting control information of DL component carriers on the UL, inaccordance with the teachings herein. At 1005, the WTRU receives firstconfiguration information for a set of UL carriers and a set of DLcarriers. The first configuration information may be included in one orseveral different messages. For example, the configuration informationfor the set of UL carriers may be received in a separate message fromthe configuration information for the set of DL carriers, or a differentsubset of UL carriers. At 1010, the WTRU configures the set of ULcarriers and the set of DL carriers according to the first configurationinformation. At 1015, the WTRU receives second configuration informationfor assigning UL carriers to carry control information for the set of DLcarriers. The assigned UL carriers may or may not be anchor or primarycarriers. The first and second configuration information may be receivedin a common message, or in separate messages. At 1020, the WTRU assignsa corresponding UL carrier to each DL carrier from the set of DLcarriers according to the second configuration information. At 1025, theWTRU receives messages over the set of DL carriers. At 1030, the WTRUtransmits control information for each DL carrier over its correspondingUL carrier. With reference to FIG. 6 , the receiving and transmitting ofcarriers may be done by a transceiver 614, and the configuration andpairing of carriers may be done by a processor 616.

Using IEEE 802.16m multicarrier operation as an example, the controlinformation for each active DL carrier may need to be reported back tothe Advanced Base Station (ABS) so that efficient frequency-selectiveand spatial scheduling may be achieved in the DL. The controlinformation for each active DL carrier may include, but is not limitedto, DL channel quality feedback, DL multi-input multi-output (MIMO)feedback, and DL HARQ ACK/NACK. For a DL carrier that has a paired ULcarrier, its feedback control information may be configured to transmiton its corresponding UL carrier. For a DL carrier that does not have apaired UL carrier, its feedback control information may be transmittedon the UL primary carrier of the Advanced Mobile Station (AMS). The ULprimary carrier may be AMS-specific.

Using LTE-A as an example, let N_(UL) and N_(DL) be the number ofaggregated carriers in the uplink and downlink, respectively. N_(UL) mayor may not be equal to N_(DL); the latter case referred to asasymmetrical carrier aggregation. Because multiple aggregated carriersare used in LTE-A, channel state information (CSI) or CQI, includingpreceding matrix index (PMI) and rank information (RI), for each DLcomponent carrier in an aggregated carrier needs to be reported back tothe eNB so that efficient frequency-selective and spatial scheduling maybe done in the DL. According to the first embodiment, PUCCHs forperiodic reporting of CSI and/or CQI for all DL component carriers areconfigured to transmit on the primary carrier in the UL. PUCCH(s) forperiodical reporting of CSI and/or CQI for all downlink carriers aretransmitted on the primary carrier designated for PUCCH transmission andmay not exist on other non-primary UL carriers. The primary carrierassigned to transmit the PUCCH(s) may carry any type of controlinformation including, but not limited to, PUCCH, CQI, CSI, PMI, RI,ACK/NACK information, HARQ feedback and scheduling requests (SR). The ULprimary carrier may be WTRU-specific, and the designation of the ULprimary carrier may be signaled to the WTRU via RRC signaling, L1signaling or MAC control element (CE). Alternatively, the primarycarrier may be cell-specific. A LTE-A WTRU may obtain the informationabout the primary carrier via acquiring the master information block(MIB) or system information block (SIB).

Optionally, PUCCHs for periodic reporting of CSI/CQI for each downlinkcarrier may be configured to transmit on a corresponding DL carrierpaired with the DL carrier. The mapping between UL carrier and DLcarrier may be WTRU-specific, and signaled to the WTRU via RRCsignaling, L1 signaling or MAC control element (CE). Alternatively, themapping between uplink carrier and downlink carrier may becell-specific. A LTE-A WTRU may obtain the information via acquiring theMIB or SIB. The mapping between uplink carrier and downlink carrier maybe fixed and specified in the standards.

Periods of CSI and/or CQI reporting of different downlink carriers maybe configured to be equal or different. For example, CSI/CQI reportingperiod of the downlink anchor carrier may be configured to be smallerthan CSI/CQI reporting periods of downlink non-anchor carriers. In otherwords, CSI/CQI reporting periods of downlink non-anchor carriers may beinteger multiples of CSI/CQI reporting period of the downlink anchorcarrier. In this way, CSI/CQI of the downlink anchor carrier isconfigured to be reported more frequently than downlink non-anchorcarriers. Whether the periods of CSI/CQI reporting of different downlinkcarriers are equal or not, the offset within a reporting period forCSI/CQI reporting for different downlink carriers may be configured tobe equal or different.

By way of example, assume that the PUCCH is mapped to a primary carrierfor all DL carriers as described above. If the anchor carrier haslimited PUCCH resources for CSI/CQI reporting, the network may configureoffsets of different carriers to be different so that the total amountof PUCCH resources in any sub-frame is minimized. Regardless of therelative reporting periodicity of the DL carriers, the systemframe/sub-frame offset may be configured so that PUCCH reporting for aparticular DL carrier does not overlap reporting for other DL carriers.Alternatively, PUCCH reporting may be staggered per DL carrier. One wayto accomplish this would be to configure the same PUCCH periodicity foreach associated DL carrier but with different subframe offsets for each.Alternatively, the periodic PUCCH may also be configured to alternatereporting for each DL carrier. The PUCCH CSI/CQI reporting may bedefined to sequentially switch according to a predetermined list of DLcarriers, or may be configured to report with a higher or lowerperiodicity for a particular carrier. For example, one DL carrier may bereported every two PUCCH frames and two other carriers may be reportedevery four PUCCH frames. In another example, in order to maintainperiodic reporting for any particular carrier, modulo 2 multiplesbetween the reporting rates may be used to fully utilize a periodicPUCCH configuration. For any of these solutions, the existence of thePUCCH transmission may be limited by the DRX or activation/deactivationstate of the associated DL carrier. When the WTRU is not receiving PDCCHon a particular DL carrier, if the primary UL carrier has plenty ofPUCCH resources to support simultaneous CSI/CQI reporting for multipledownlink carriers, the network may configure offsets of differentcarriers to be the same so that PUCCHs for different carriers' CSI/CQIreporting are aligned. In this way, the DRX cycle oractivation/deactivation state has a low impact on CSI/CQI reporting formultiple downlink carriers.

Although multiple aggregated carriers are used in LTE-A, only one totalWTRU data transmission buffer may be maintained. Hence, based on bufferoccupancy, only one scheduling request (SR) may be required for the eNBso that uplink channel resources may be scheduled for the WTRU. PUCCHfor SR reporting may be configured using the following methods. In oneembodiment, PUCCH reporting of SR is configured to be periodic and istransmitted on a primary carrier in the UL. PUCCH(s) reporting of SR maynot exist on non-primary UL carriers. The UL primary carrier may beWTRU-specific, and signaled to the WTRU via RRC signaling, L1 signalingor MAC control element (CE). WTRU specific UL and DL primary carriersallow for improved load balancing across UL and DL carriers.Alternatively, the primary carrier may be cell-specific. A LTE-A WTRUmay obtain the information about the primary carrier via acquiringmaster information block (MIB) or system information block (SIB). In thecell specific case, all WTRUs with the same primary DL carrier may havethe same primary UL carrier. The default mode of operation may use acell-specific UL primary carrier until a WTRU-specific RRCreconfiguration procedure is applied.

In another embodiment, the PUCCH reporting of SR may be configured to beperiodic and may be transmitted on a set of uplink carriers, where theset may include more than one carrier but may be less than the set ofall UL carriers. The periods and offset for PUCCHs mapped on differentuplink carriers may be configured to be the same or different. If PUCCHsfor SR reporting of a WTRU are configured on several uplink carriers inthe same sub-frame, the WTRU may transmit on one or a subset of thosePUCCHs, which may be specified by the standards.

For PUCCH for SR reporting, it is assumed that the network may determinethe UL carrier of the uplink shared channel (UL_SCH) allocation.Alternatively, the WTRU may request UL_SCH resources by transmitting aSR on the UL carrier for which UL resources are requested. In this way,the WTRU may dynamically request an UL_SCH allocation on particular ULcarriers. The decision criteria for generating a SR on a particular ULcarrier may be traffic volume based and/or relative to the ability ofallocations on other UL carriers to support the current UL transmissionrequirement.

For IEEE 802.16m, with the multicarrier operation, a carrier may beassigned to carry physical (PHY) and/or medium access (MAC) controlsignaling in addition to data traffic, referred to as a primary carrier,for each Advanced Mobile Station. In TDD mode, one carrier may be usedas the primary carrier for both DL and UL. In FDD mode, a DL carrier andan UL carrier may be used as a DL primary carrier and an UL primarycarrier, respectively. In accordance with the teachings herein, theprimary carrier of an AMS may be changed dynamically. Furthermore, thedynamic changing methods disclosed herein may be applied to any of theUL or DL carriers, and any new set of UL and/or DL carriers may beassigned in a dynamic or semi-persistent manner. The dynamic changingmethods disclosed herein may be applied to both UL and DL carrierstogether, or to UL or DL carriers separately in a unidirectionalhandover procedure.

For each of the primary or anchor carrier methods described herein, theUL primary carrier, anchor carrier or any other carrier may be switchedwithin the configured set of UL carriers. The switching may be initiatedby either the WTRU or eNB, and signaled by either RRC, MAC or physicalcontrol signaling methods. In this case, the switching may be part of anintra-cell handover procedure. Additionally, the UL primary carrier,anchor carrier or any other carrier may be switched to an UL carrierthat is not part of the currently configured set of UL carriers withinthe current cell. In this case, the switching may be part of aninter-cell handover procedure. The procedure may be initiated by eitherthe eNB or the WTRU.

For LTE-A, an UL carrier may be assigned to carry PUCCH, referred to asa primary carrier or UL anchor carrier, similar to the DL anchor carriercarrying the physical downlink control channel (PDCCH). A primarycarrier may be an UL anchor carrier or any other UL carrier. The DLanchor carrier(s) and UL primary carrier(s), including UL anchorcarriers, may also be used for carrying HARQ feedback, SRs, and CQI/CSI,among other information. Other non-primary UL carriers may not be usedfor carrying HARQ feedback, SR and CQI/CSI, among other information. Inaccordance with the teachings herein, the DL anchor carrier(s) and ULprimary carrier(s), including UL anchor carriers, may be switcheddynamically. Furthermore, the dynamic switching methods disclosed hereinmay be applied to any of the UL or DL carriers, and any new set of ULand/or DL carriers may be assigned in a dynamic or semi-persistentmanner. The dynamic switching methods disclosed herein may be applied toboth UL and DL carriers together, or to UL or DL carriers separately ina unidirectional handover or carrier reconfiguration procedures.

A WTRU may switch DL and/or UL carriers, including anchor carriers orprimary carriers, during the WTRUs normal operations without handover,or during a handover. Handovers may be either inter-cell or intra-cell,and may be controlled by an eNB or the WTRU may initiate forwardhandovers. The switching of the DL and/or UL carriers may be dynamic,which is considered fast, or semi-persistent, which is consideredslower. The DL and/or UL component carrier switching at the WTRU may betriggered by DL signaling from an eNB or based on preconfiguredswitching or a hopping pattern. The triggering of DL anchor carrierswitching may be eNB or WTRU initiated. The reassignment of the DLprimary or anchor carrier may be to a carrier within the current set ofDL carriers being received by the WTRU or to a new DL carrier notcurrently part of the set of active DL carriers for that WTRU. When thenew primary or anchor carrier assignment is within the current set ofactive DL carriers, the WTRU reconfiguration procedure may be optimizedso that reset and reestablishment of RLC and PDCP protocols are notrequired.

Methods for dynamic and semi-persistent switching and unidirectionalhandover are discussed in detail hereinafter, and may be applied to anykind of carrier including primary carriers, anchor carriers, non-anchorcarriers or any active carrier in both the UL and DL directions. Methodsdescribed with respect to anchor carriers may interchangeably be appliedto primary carriers or non-anchor carriers, and vice versa.

The switching of DL and/or UL component carriers may follow manypossible patterns. According to one pattern, the switching is from onecomponent carrier to another component carrier. According to anotherpattern, the switching may be from one component carrier to anothersubset of carriers, which may or may not include the triggering carrierthat may be an anchor or primary carrier. Alternatively, the switchingmay be from one component carrier to all component carriers. In anotherpattern, the switching may be from one subset of component carriers orall component carriers to one component carrier that may be the anchoror primary carrier. According to another pattern, the switching may befrom a subset of component carriers to another subset of componentcarriers or all component carriers in a DL or UL direction. In yetanother pattern, the switching may be from all component carriers in aDL or UL direction to a subset of component carriers.

Switching a set of carriers by increasing in the number of carriers isreferred to as expansion. Similarly, switching a set of carrier bydecreasing the number of carriers is referred to as contraction. DLand/or UL component carrier switching or expansion may be signaled usingRRC and/or L1/L2 signaling; for example, the PDCCH, the PUCCH, or themedium access control (MAC) layer may be used. An RRC message may beused to signal the switch, or the MAC control element (CE) and the PDCCHmay be used to carry the switching signaling to the WTRU. An RRC messagemay be used to provide component carrier configurations, and the PDCCHor MAC CE may be used to signal the switch. The ability to usePDCCH/PUCCH and/or MAC CE signaling may also be used for just intra-cellcarrier switching. Switching the UL or DL anchor carrier(s) or primarycarrier(s) may be within the current set of active carriers. An RRCmessage may also be used to signal the switching or hopping pattern forthe WTRU to follow and for inter-cell handovers. Hopping and DLsignaling may be used to trigger component carrier switching, where asignal may be transmitted from the eNB to the WTRU through the PDCCH orMAC CE from the time when the WTRU uses a hopping approach. Hopping andDL signaling may start when the WTRU switches the component carrierbased on DL signaling. The WTRU may send the acknowledgement to thecarrier switch message in order to maintain alignment of active carriersbetween the WTRU and the eNB when the PDCCH or MAC CE are used to signalcarrier switching. Also, a time synchronized switch on a sub-frameboundary may be defined relative to PDCCH or MAC CE reception.

According to one embodiment, the switching of DL and/or UL componentcarriers may be from one component carrier to another component carrier.This may occur when the WTRU switches from one anchor carrier to anotheranchor carrier. The PDCCH or the MAC CE may be used to signal the switchto the WTRU. If the switch occurs during handover, the RRC messagecontained in the handover command may be used to signal the anchorcarrier switch from one cell to another cell. The message containedinside the PDCCH or MAC CE or handover command may include any or all ofthe following information: a starting transmission time interval (TTI),for example, the system frame number (SFN) for the WTRU to monitor inorder to capture the new DL anchor carrier or transmit on the new ULcarrier; the TTI (for example, the SFN) to be disconnected by the WTRUfor the existing UL/DL anchor carrier; how long the WTRU may stay on thenew DL/UL anchor carrier and the subsequent anchor carrier that the WTRUwill listen to; and a trigger to start an inactivity timer or anon-duration timer for discontinuous reception (DRX) on the new anchorcarrier. When switching anchor carriers, the configuration for differentcarriers may be maintained. Optionally, the configuration for somecarriers may change.

Besides using PDCCH or MAC CE to trigger the switching from an existinganchor carrier to another anchor carrier, switching may also follow ahopping pattern which may be signaled via an RRC message. The eNB mayuse the PDCCH or MAC CE to signal the WTRU to terminate the carrierhopping pattern and request that the WTRU follows the informationcontained on the PDCCH or the MAC CE to trigger the carrier switching.Alternatively, the eNB may use the PDCCH or MAC CE to activate carrierswitching following the hopping pattern signaled by RRC message.

According to another embodiment, the switching of DL and/or UL componentcarriers may be from one component carrier to another subset ofcarriers, which may not include the triggering carrier and may be theanchor carrier only, which may be a primary carrier, or all componentcarriers. This may occur when there is DL data necessitating more DLcomponent carriers to be activated by the anchor carrier, which aspreviously stated may be a primary carrier. Activation of other DLcomponent carriers may be through the PDCCH or the MAC CE. The PDCCH orMAC CE may also contain an indicator as to which DL component carriersmay be activated. The parameters for the carriers to be activated may ormay not be the same for each carrier. For example, the inactivity timerfor each component carrier may be different. A subset of carriers may beactivated at the same time, but depending on the DL transmissionactivity, certain component carriers may be deactivated by the anchorcarrier via the PDCCH or MAC CE. Each of this subset of componentcarriers may go to sleep autonomously if the DL transmission on thatcarrier is successfully completed. If this occurs during handover, theactivation message may be contained in the handover command.

According to another embodiment, the switching of DL and/or UL componentcarriers may be from one subset of component carriers or all componentcarriers to one component carrier, for example, the anchor carrier,which may be a primary carrier. This may occur when some or all of thecomponent carriers are activated from a dormant state for datatransmission, then finish the transmission and return to a sleep mode.The switch to deactivate the carriers may be signaled through the PDCCHor MAC CE for each of the subset of component carriers except the anchor(or primary) carrier. Alternatively, the carriers, other than the anchorcarrier, may deactivate autonomously upon the expiration of one or moretimers. Alternatively, the message may only be contained in PDCCH or MACCE on the anchor carrier. During this switch, the anchor carrier thatremains may be different from the anchor carrier that activates thesubset of component carriers. If this occurs during handover, theactivation message may be contained in the handover command.

According to another embodiment, the switching of DL and/or UL componentcarriers may be from a subset of component carriers to another subset ofcomponent carriers or to all component carriers. Similarly, theswitching may be from all component carriers to a subset of componentcarriers. The switch may be signaled through the PDCCH or MAC CE on theanchor carrier to the WTRU. Optionally, the message from all activecomponent carriers may be contained in the PDCCH or the MAC CE. Once aWTRU receives the message, the WTRU may deactivate certain componentcarriers and activate other carriers according to what is beingsignaled. If this occurs during handover, the activation message may becontained in the handover command. The switching may also occur based ona preconfigured hopping pattern signaled via RRC message.

Switching of the anchor carrier and the active set of carriers may beapplied in an inter-cell handover. Any one active UL or DL carrier maybe reassigned to be the anchor carrier with PDCCH/PUCCH, or MAC CEsignaling without requiring RRC reconfiguration. An explicit signalconfirmation may be sent through a HARQ acknowledge signal, althoughimplicit confirmation is also possible, for example by detecting areassignment of PDCCH or PUCCH for the WTRU on the particular carrier.Existing configurations may be transferred to the new anchor carrier.The configurations may be beyond the PDCCH and PUCCH configurations andinclude, for example, the DRX cycles and associated timers, thesemi-persistent scheduling configuration, the HARQ entity/processassignment and other configurations.

For an intra-cell handover, switching of the anchor or primary carrier,or set of active carriers may be applied for just UL carriers or just DLcarriers. This may be considered a unidirectional handover. Only theconfiguration and operation in that direction is affected by the carrierswitching. The carrier switching criteria may be, for example, carrierquality measurements or traffic congestion. The WTRU may use the radiolink failure (RLF) procedure or, the eNB may use sound reference signal(SRS) or channel quality measurement (CQI) reception to invoke theprocedure. The WTRU may detect RLF on one or more DL component carriersand choose to invoke a DL carrier switching procedure. This DL switchingprocedure may be uniquely applied to the DL anchor or primary carrier.WTRU-initiated procedure may be accomplished either by RRC, MAC CE, orPUCCH signaling. The eNB may detect criteria for UL component carrierswitching from SRS reception on each of the configured UL carriers, ordetect criteria for DL component carrier switching from DL CQI reportingreceived on the UL primary component carrier. The eNB initiated UL or DLcomponent carrier (CC) switching procedures may be accomplished by RRC,MAC CE, or PDCCH signaling.

FIGS. 11A, 11B, 12A and 12B show examples of carrier switching on acommon eNB. In FIGS. 11A and 11B, DL carriers 1110 _(A), 1110 _(B), and1110 _(C) and UL carriers 1112 _(A), 1112 _(B), and 1112 _(C) areconfigured between the eNB 1102 and the WTRU 1106. DL carriers 1110_(A), 1110 _(B), and 1110 _(C) and UL carriers 1112 _(A), 1112 _(B), and1112 _(C) may include anchor carriers, primary carriers and non-anchorcarriers. In FIGS. 11A and 11B, transmissions exist on any carrier, 1110_(A), 1110 _(B), 1110 _(C), 1112 _(A), 1112 _(B), and 1112 _(C) that arecurrently configured, activated and have a valid DL schedulingallocation or UL grant. In FIG. 11A, a DL primary or anchor carrier isconfigured on DL carrier 1110 _(A), and a UL primary or anchor carrieris configured on UL carrier 1112 _(B), as indicated by shading. In FIG.11B, the UL primary carrier that previously existed on UL carrier 1112_(B) is switched to UL carrier 1112 _(C) within the set of configuredcarriers. For example, UL primary or anchor carrier 1112 _(B) may beswitched to new UL primary or anchor carrier 1112 _(C). Switching in theUL and DL may occur independently, or unidirectionally, such that a DLcarrier may not be switched when an UL carrier is switched.

Similarly, in FIGS. 12A, and 12B, DL carriers 1210 _(A), 1210 _(B), and1210 _(C) and UL carriers 1212 _(A), 1212 _(B), and 1212 _(C) areconfigured between the eNB 1202 and the WTRU 1206. DL carriers 1210_(A), 1210 _(B), and 1210 _(C) and UL carriers 1212 _(A), 1212 _(B), and1212 _(C) may include anchor carriers, primary carriers and non-anchorcarriers. In FIG. 12A, and 12B, transmissions exist on any carrier, 1210_(A), 1210 _(B), 1210 _(C), 1212 _(A), 1212 _(B), and 1212 _(C) that arecurrently configured, activated and have a valid DL schedulingallocation or UL grant. In FIG. 12A, a DL primary or anchor carrier isconfigured on DL carrier 1210 _(A), and a UL primary or anchor isconfigured UL carrier 1212 _(B), as indicated by shading. In FIG. 12B,the DL primary carrier that previously existed on DL carrier 1210 _(A)are switched to DL carrier 1210 _(C) within the set of configuredcarriers. For example, DL primary or anchor carrier 1210 _(A) may beswitched to new DL primary or anchor carrier 1210 _(C). Switching in theUL and DL may occur independently, or unidirectionally, such that an ULcarrier may not be switched when a DL carrier is switched.

FIGS. 11A, 11B, 12A, and 12B, illustrate examples of carrier switchingon a common eNB within the set of existing configured carriers. In theseexamples a primary or anchor carrier is switched within the set ofcurrently configured carriers. In a similar manner, carriers may beswitched outside the set of previously configured carriers, byconfiguring a new carrier and then executing the switch. Moreover, theset of configured carriers may be expanded or contracted during acarrier switch. Similar procedures may be applied to non-primary ornon-anchor carriers.

FIGS. 13A, 13B, 14A and 14B show examples of carrier switching from oneeNB to another eNB, referred to as unidirectional handovers. In FIGS.13A and 13B, DL carriers 1310 _(A), 1310 _(B), and 1310 _(C) and ULcarriers 1312 _(A), 1312 _(B), and 1312 _(C) are configured between theeNB 1302 and the WTRU 1306. Also, DL carrier 1310 _(D) is configuredbetween the eNB 1304 and the WTRU 1306. DL carriers 1310 _(A), 1310_(B), 1310 _(C), and 1310 _(D) and UL carriers 1312 _(A), 1312 _(B), and1312 _(C) may include anchor carriers, primary carriers and non-anchorcarriers. In FIGS. 13A and 13B, transmissions exist on any carrier, 1310_(A), 1310 _(B), 1310 _(C), 1310 _(D) 1312 _(A), 1312 _(B), and 1312_(C) that are currently configured, activated and have a valid DLscheduling allocation UL grant. In FIG. 13A, a DL primary or anchorcarrier is configured DL carrier 1310 _(A), and a UL primary or anchoris configured UL carrier 1312 _(C), as indicated by shading. In FIG.13B, the DL primary carrier that previously existed on DL carrier 1310_(A) are switched to configured DL carrier 1310 _(D) on eNB 1304 as partof a unidirectional handover. For example, DL primary or anchor carrier1310 _(A) may be switched to new DL primary or anchor carrier 1310 _(D)on new eNB 1304. Switching in the UL and DL may occur independently, orunidirectionally, such that a DL carrier may not be switched when an ULcarrier is switched.

In FIGS. 14A and 14B, DL carriers 1410 _(A), 1410 _(B), and 1410 _(C)and UL carriers 1412 _(A), 1412 _(B), and 1412 _(C) are configuredbetween the eNB 1402 and the WTRU 1406. Also, UL carrier 1412 _(D) isconfigured between the eNB 1404 and the WTRU 1406. DL carriers 1410_(A), 1410 _(B), 1410 _(C), and 1410 _(D) and UL carriers 1412 _(A),1412 _(B), and 1412 _(C) may include anchor carriers, primary carriersand non-anchor carriers. In FIGS. 14A and 14B, transmissions exist onany carrier, 1410 _(A), 1410 _(B), 1410 _(C), 1412 _(A), 1412 _(B), 1412_(C) and 1412 _(D) that are currently configured, activated and have avalid DL scheduling allocation or UL grant. In FIG. 14A, a DL primary oranchor carrier is configured DL carrier 1410 _(A), and a UL primary oranchor carrier is configured UL carrier 1412 _(C), as indicated byshading. In FIG. 14B, the UL primary carrier that previously existed onUL carrier 1412 _(C) are switched to configured UL carrier 1412 _(D) oneNB 1404 as part of a unidirectional handover. For example, UL primaryor anchor carrier 1412 _(C) may be switched to new UL primary or anchorcarrier 1412 _(D) on new eNB 1404. Switching in the UL and DL may occurindependently, or unidirectionally, such that a DL carrier may not beswitched when an UL carrier is switched.

FIGS. 13A, 13B, 14A and 14B illustrate examples of carrier switchingbetween different eNBs (i.e. unidirectional handovers) within the set ofexisting configured carriers. In these examples a primary or anchorcarrier is switched within the set of currently configured carriers. Ina similar manner, carriers may be switched outside the set of previouslyconfigured carriers, by configuring a new carrier on the target eNB andthen executing the switch. Moreover, the set of configured carriers maybe expanded or contracted during a carrier switch, on either theexisting eNB or target eNB. It should also be noted that similarprocedures may be applied to non-primary or non-anchor carriers.

Although features and elements are described above in particularcombinations, each feature or element can be used alone without theother features and elements or in various combinations with or withoutother features and elements. The methods or flow charts provided hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) or Ultra Wide Band (UWD)module.

1-34 (canceled)
 35. A base station comprising: a processor configured toat least: transmit, to a wireless transmit/receive unit (WTRU), a firstradio resource control (RRC) message comprising a first configurationinformation that indicates a primary uplink (UL) carrier to be used tocarry a first control type information, wherein the first control typeinformation is associated with at least one downlink (DL) carrier of afirst set of DL carriers; receive, from the WTRU, the first control typeinformation associated with the at least one DL carrier of the first setof DL carriers via a physical uplink control channel (PUCCH)transmission on the primary UL carrier; transmit, to the WTRU, a secondRRC message comprising a second configuration information that indicatesa non-primary UL carrier to carry a second control type information,wherein the second control type information is associated with at leastone DL carrier of a second set of DL carriers; and receive, from theWTRU, the second control type information associated with the at leastone DL carrier of the second set of DL carriers via a PUCCH transmissionon the non-primary UL carrier.
 36. The base station of claim 35, whereinthe first control type information associated with the at least one DLcarrier of the first set of DL carriers or the second control typeinformation associated with the at least one DL carrier of the secondset of DL carriers comprises one or more of a hybrid automatic request(HARD) feedback, a channel quality information (CQI), or a channel stateinformation (CSI).
 37. The base station of claim 35, wherein theprocessor is configured to transmit a medium access control (MAC)control element (CE) indicating activation of the non-primary ULcarrier.
 38. A method implemented by a base station, the methodcomprising: transmitting, to a wireless transmit/receive unit (WTRU), afirst radio resource control (RRC) message comprising a firstconfiguration information that indicates a primary uplink (UL) carrierto be used to carry a first control type information, wherein the firstcontrol type information is associated with at least one downlink (DL)carrier of a first set of DL carriers; receiving, from the WTRU, thefirst control type information associated with the at least one DLcarrier of the first set of DL carriers via a physical uplink controlchannel (PUCCH) transmission on the primary UL carrier; andtransmitting, to the WTRU, a second RRC message comprising a secondconfiguration information that indicates a non-primary UL carrier tocarry a second control type information, wherein the second control typeinformation is associated with at least one DL carrier of a second setof DL carriers; and receive, from the WTRU, the second control typeinformation associated with the at least one DL carrier of the secondset of DL carriers via a PUCCH transmission on the non-primary ULcarrier.
 39. The method of claim 38, wherein the first control typeinformation associated with the at least one DL carrier of the first setof DL carriers or the second control type information associated withthe at least one DL carrier of the second set of DL carriers comprisesone or more of a hybrid automatic request (HARD) feedback, a channelquality information (CQI), or a channel state information (CSI).
 40. Themethod of claim 38, further comprising transmitting a medium accesscontrol (MAC) control element (CE) indicating activation of thenon-primary UL carrier.